Too hot, too tough, too crowded: Abiotic and biotic constraints on Niphograpta albiguttalis establishment on water hyacinth (Pontederia crassipes) in the southeastern United States

Authors: MARIANI, FLAMINIA - Louisana State University; STEEN, EMILY - Louisiana State University; Rector, Brian; Pratt, Paul; DIAZ, RODRIGO - Louisana State University

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2026
Publication Date: 3/25/2026
Citation: Mariani, F., Steen, E.G., Rector, B.G., Pratt, P.D., Diaz, R. 2026. Too hot, too tough, too crowded: Abiotic and biotic constraints on Niphograpta albiguttalis establishment on water hyacinth (Pontederia crassipes) in the southeastern United States. Biological Control. 216. Article 106023. https://doi.org/10.1016/j.biocontrol.2026.106023.
DOI: https://doi.org/10.1016/j.biocontrol.2026.106023

Interpretive Summary: The water hyacinth moth (Niphograpta albiguttalis, WHM) was introduced from Argentina to the United States in the 1970s for biological control of water hyacinth, an invasive aquatic weed that chokes waterways in the southeastern USA and California and incurs millions of dollars annually in control costs. While it established in southeastern states, populations failed to persist elsewhere. To identify factors constraining establishment, experiments were conducted to deetrmine if establishment was limited by (I) abiotic factors (e.g. water temperature, conductivity, nutrients), (II) host-plant traits (petiole toughness, tissue nitrogen, C:N ratio, growth form, mat position), or (III) biotic interactions with other herbivores (weevils or mites).  Twenty-two sites were surveyed across Louisiana, Mississippi, Alabama, Texas, and Florida, spanning 8° latitude. The WHM was detected in 6 of 22 sites (27%). Sites with WHM had cooler waters, higher nitrate concentrations, softer petioles, and higher tissue nitrogen. WHM was also more abundant in mat interiors. However, even at the most abundant sites, WHM densities remained low, averaging 0.10 ± 0.01 larvae per plant. WHM was also less abundant in the presence of other arthtopod herbivores. Our findings indicate that establishment of N. albiguttalis is constrained by the interplay of abiotic factors, host-plant traits, and biotic interactions, informing future WHM release strategies in California and elsewhere.

Technical Abstract: The water hyacinth moth Niphograpta albiguttalis was introduced from Argentina to the United States in the 1970s for biological control of water hyacinth, an invasive aquatic weed that chokes waterways in the southeastern USA and California and incurs millions of dollars annually in control costs. While it established in southeastern states, populations failed to persist elsewhere. To identify factors constraining establishment, experiments were conducted to deetrmine if establishment was limited by (I) abiotic factors (e.g. water temperature, conductivity, nutrients), (II) host-plant traits (petiole toughness, tissue nitrogen, C:N ratio, growth form, mat position), or (III) biotic interactions with other herbivores (weevils or mites). N. albiguttalis was detected in 6 of 22 sites (27%). Sites with N. albiguttalis had cooler waters (25.5 ± 4.1 °C vs. 28.8 ± 1.6 °C), higher nitrate concentrations (3.83 ± 0.67 vs. 2.11 ± 0.72 mg L'¹), softer petioles (1.72 ± 0.79 vs. 2.57 ± 1.20 N), and higher tissue nitrogen (2.74 ± 0.76% vs. 1.94 ± 0.62%). Even at the most abundant sites, moth densities remained low, averaging 0.10 ± 0.01 larvae per plant. Generalized models for presence (AICc = 627.2) and density (AICc = –2756.53) of N. albiguttalis showed strong fit and identified the same drivers: higher occurrence in cooler, nitrate-rich waters, on softer plants within mat interiors; both were reduced by feeding damage from co-occurring herbivores. Our findings indicate that establishment of N. albiguttalis is constrained by the interplay of abiotic factors, host-plant traits, and biotic interactions. These insights provide a strong basis for improving establishment of future releases.. We surveyed 22 sites across Louisiana, Mississippi, Alabama, Texas, and Florida, spanning 8° latitude. At each site, we measured water properties , plant traits, and herbivore damage (from Neochetina spp. and Orthogalumna mites). N. albiguttalis was detected in 6 of 22 sites (27%). Sites with N. albiguttalis had cooler waters (25.5 ± 4.1 °C vs. 28.8 ± 1.6 °C), higher nitrate concentrations (3.83 ± 0.67 vs. 2.11 ± 0.72 mg L'¹), softer petioles (1.72 ± 0.79 vs. 2.57 ± 1.20 N), and higher tissue nitrogen (2.74 ± 0.76% vs. 1.94 ± 0.62%). Even at the most abundant sites, moth densities remained low, averaging 0.10 ± 0.01 larvae per plant. Generalized models for presence (AICc = 627.2) and density (AICc = –2756.53) of N. albiguttalis showed strong fit and identified the same drivers: higher occurrence in cooler, nitrate-rich waters, on softer plants within mat interiors; both were reduced by feeding damage from co-occurring herbivores. Our findings indicate that establishment of N. albiguttalis is constrained by the interplay of abiotic factors, host-plant traits, and biotic interactions. These insights provide a strong basis for improving establishment of future releases.